Conserved gene cluster at replication origins of the alpha-proteobacteria Caulobacter crescentus and Rickettsia prowazekii.
(17/209)
A 30-kb region surrounding the replication origin in Caulobacter crescentus was analyzed. Comparison to the genome sequence of another alpha-proteobacterium, Rickettsia prowazekii, revealed a conserved cluster of genes (RP001, hemE, hemH, and RP883) that overlaps the established origin of replication in C. crescentus and the putative origin of replication in R. prowazekii. The genes flanking this cluster differ between these two organisms. We therefore propose that this conserved gene cluster can be used to identify the origin of replication in other alpha-proteobacteria. (+info)
Epidemic typhus meningitis in the southwestern United States.
(18/209)
A patient residing in New Mexico had murine typhus diagnosed. A novel molecular assay was performed at the Centers for Disease Control and Prevention, and Rickettsia prowazekii, the agent of epidemic typhus, was found, rather than R. typhi. To our knowledge, this is the first reported case of epidemic typhus confirmed by means of polymerase chain reaction--based testing of cerebrospinal fluid, and it introduces a novel assay for the molecular diagnosis of both epidemic and murine typhus. (+info)
Phylogenetic analysis of the rompB genes of Rickettsia felis and Rickettsia prowazekii European-human and North American flying-squirrel strains.
(19/209)
The rickettsial outer membrane protein B (rompB) gene encodes the major surface antigens of Rickettsia species. We undertook sequencing and molecular analysis of the rompB gene of Rickettsia felis and a comparison with its homologs in spotted fever group (SFG) and typhus group (TG) rickettsiae, including the complete sequences of two North American flying squirrel strains and two European human strains of Rickettsia prowazekii. We sequenced 5,226 base pairs (bp) of the R. felis rompB, encoding a protein of 1,654 amino acids. We also sequenced 5,015 bp of rompB of the flying squirrel strains, encoding a protein of 1,643 amino acids. Analysis of the R. felis rompB gene sequence showed 10-13% divergence from SFG rickettsiae and 18% divergence from the TG rickettsiae. The rompB of all sequenced strains of R. prowazekii showed an overall similarity of 99.7-99.9%. (+info)
Pseudogenes, junk DNA, and the dynamics of Rickettsia genomes.
(20/209)
Studies of neutrally evolving sequences suggest that differences in eukaryotic genome sizes result from different rates of DNA loss. However, very few pseudogenes have been identified in microbial species, and the processes whereby genes and genomes deteriorate in bacteria remain largely unresolved. The typhus-causing agent, Rickettsia prowazekii, is exceptional in that as much as 24% of its 1.1-Mb genome consists of noncoding DNA and pseudogenes. To test the hypothesis that the noncoding DNA in the R. prowazekii genome represents degraded remnants of ancestral genes, we systematically examined all of the identified pseudogenes and their flanking sequences in three additional Rickettsia species. Consistent with the hypothesis, we observe sequence similarities between genes and pseudogenes in one species and intergenic DNA in another species. We show that the frequencies and average sizes of deletions are larger than insertions in neutrally evolving pseudogene sequences. Our results suggest that inactivated genetic material in the Rickettsia genomes deteriorates spontaneously due to a mutation bias for deletions and that the noncoding sequences represent DNA in the final stages of this degenerative process. (+info)
Rickettsial hemolysis: rapid method for enumeration of metabolically active typhus rickettsiae.
(21/209)
A new assay is described for enumerating biologically active typhus rickettsiae (Madrid E strain), based on adsorption of rickettsiae to erythrocytes in the presence of NaF (which allows adsorption but not lysis) and lysis in the presence of anti-Rickettsia prowazeki immune serum (which allows only a single round of lysis). The number of lysed erythrocytes is then used to estimate the number of active rickettsiae. (+info)
Mutualists and parasites: how to paint yourself into a (metabolic) corner.
(22/209)
Eukaryotes have developed an elaborate series of interactions with bacteria that enter their bodies and/or cells. Genome evolution of symbiotic and parasitic bacteria multiplying inside eukaryotic cells results in both convergent and divergent changes. The genome sequences of the symbiotic bacteria of aphids, Buchnera aphidicola, and the parasitic bacteria of body louse and humans, Rickettsia prowazekii, provide insights into these processes. Convergent genome characteristics include reduction in genome sizes and lowered G+C content values. Divergent evolution was recorded for amino acid and cell wall biosynthetic genes. The presence of pseudogenes in both genomes provides examples of recent gene inactivation events and offers clues to the process of genome deterioration and host-cell adaptation. (+info)
The origin and early evolution of mitochondria.
(23/209)
Complete sequences of numerous mitochondrial, many prokaryotic, and several nuclear genomes are now available. These data confirm that the mitochondrial genome originated from a eubacterial (specifically alpha-proteobacterial) ancestor but raise questions about the evolutionary antecedents of the mitochondrial proteome. (+info)
Mechanisms of evolution in Rickettsia conorii and R. prowazekii.
(24/209)
Rickettsia conorii is an obligate intracellular bacterium that causes Mediterranean spotted fever in humans. We determined the 1,268,755-nucleotide complete genome sequence of R. conorii, containing 1374 open reading frames. This genome exhibits 804 of the 834 genes of the previously determined R. prowazekii genome plus 552 supplementary open reading frames and a 10-fold increase in the number of repetitive elements. Despite these differences, the two genomes exhibit a nearly perfect colinearity that allowed the clear identification of different stages of gene alterations with gene remnants and 37 genes split in 105 fragments, of which 59 are transcribed. A 38-kilobase sequence inversion was dated shortly after the divergence of the genus. (+info)